Automatic choke control



March 28, 1939. E MOORE 2,152,078

AUTOMATIC CHOKE CONTROL Filed y 13, 1952 N VENTORQ Bggaf W Patented Mar.28 1939 2,152,078 7 AUTOMATIC CHOKE CONTROL Earl El Moore, South Bend,Ind., assignor, by

mesne assignments, to

ration, South Bend, ware Bendix AviationCorpo- Ind., a. corporation ofDela Application May 13, 1932, Serial No. 611,109

1 Claim.

This invention relates to an automatic choke control and has for. itsprincipal object the provision of simplified means for automaticallycontrolling the choke valve of an internal combustion engine carburetorin accordance with the temperature of the engine;

A further object lies in theprovision of means which will automaticallyprovide a rich mixture. of

fuel and air for starting purposes, but which will not so enrich thefuel mixture at such time as to cause the engine to load up or fail toexplode some of the fuel charges by reason of the fuel mixture being toorich for the tion.

A still further object lies in the provision of a device of thecharacter described which is simple and economical to manufacture, easyto install, and which will not readily get out of order in use.

Other objects and advantages of the invention will appear as thedescription proceeds.-

particular operating condi- The accompanying drawing shows a single airintake as indicated by the line 2-2 on Figure 1, showing the carburetorchokevalve in" open position.

Figure 3 is a sectional view on the line 3-3 of Figure 2.

Referring to the drawing in detail and particularly to Figure 1,the'numeral l generally indicates an internal combustion engine blockcarrying a cylinder head ll secured to the block by means of stud boltsi2 and carrying an exhaust manifold I4 and an intake manifold l5 held inplace thereon by means of stud bolts Hi. The cylinder head ll carriesspark plugs I! connected with a conventional ignition system, not shown,in the usual manner. A carburetor generally indicated at 20 is connectedto the lower end of an intake passage 2| which extends through theexhaust manifold l4 and into the intake manifold l5. The carburetor 20is provided with a gas intake line 23, an air intake 25, a throttlevalve shaft 26 connected by a lever arm 21 with a'reciprocating linkmember 28 which extends to manual control devices, not illustrated. Inthe air intake thereof the carburetor is provided with a choke valve 30'particularly illustrated in Figure 3, mounted upon a shaft 32 journaledin the side wallsof the air intake 25. One end of the shaft '32 extendsoutwardly beyond the walls of the air intake and upon this extending endthere is mounted a lever arm generally indicated at 34 adapted toactuate the choke valve 30 from its open to its closed position and viceversa. A coiled thermostat 35 is mounted upon a shaft 36 journaled in ahollow casing 38 which is secured to the exhaust manifold l4 by means ofan apertured lug 39 and a stud bolt 40, or by other equivalent securingmeans. The inner end of the thermostat is non-rotatably secured upon theshaft 36 by means .of the construction illustrated in Figure 1, in whichthe bent-over inner end of the thermostat is retained in a diametricalslot provided in the shaft. The outer end of the thermostat is bentoutwardly as at 4| and bears against a stop 42 which may comprise atongue stuck out of the side of the casing 38, and bent inwardly toengage the outwardly bent end 4| of the thermostat. It is to beunderstood, however, that various equivalent stop devices may beprovided and that the stop may be made adjustable if desired. One end ofthe shaft 36 projects outof the casing 38 1 and upon this outwardlyprojecting enda lever arm 45 is non-rotatably mounted by means of atightening screw 46 extending through ears provided upon a split end ofthe'lever, or by other equivalent means.

The lever arm generally indicated at 34 which is mounted upon the shaft32 of the choke valve is formed as a bell-crank lever having a long arm48' and a short arm 49 extending upon substantially opposite sides ofthe shaft 32. The lever is provided with an aperture for the shaft 32and with a slotted portion communicating with the aperture and providedwith apertured ears through which extends a tightening screw 50 fordrawing the aperture through which the shaft 32 extends, closely aboutthe shaft to non-rotatably secure the lever arm 34 upon the end of theshaft f32 The longer end 48 of the lever 34 carries at its free endapivotally mounted block 52 through which extends a substantiallydiametric aperture,

and a link member 55, having its upper end pivotally secured to the freeend of the lever 45, projects at its lower end through the aperture inthe block 52, the block 52 being adjustably secured upon the lower endof the link by means of a set screw 51. The invention, however, is notlimited to this particular form of linkage as it is apparent as aflexible member or chain, could be employed two armed lever.

with substantially the same results.

From this description, it will be observed that as the thermostat 35tends to wind up and unwind due to changes in the temperature thereof,it will actuate the arm 45, the link 55 and the arm 34 to urge the chokevalve 30 from its open toward its closedposition or vice versa.

From a further inspection of Figure 1, it will be observed that thethrottle lever 21 is provided in addition to the throttle actuation partwith a downwardly extending portion 60, which is preferably formedintegral therewith to form a The outer end of the member 60 is providedwith an aperture by means of which a block 65 is pivotally secured tothe member. aperture through which extends one end of a link member 61the other end of whichis bent over and engaged in an aperture 58provided in the end of the short portion 49 of the bell-crank lever 34.The end of the link 61 projects beyond the block 65 and upon thisprojecting end there is secured a clamp H! held in position on the linkby means of a screw 12 to provide an over-travel connection between thelink 61' and the end of the member 60. It will be apparent in thisinstance also that various equivalent connecting means including aflexible member, chain, or Bowden wire may be used.

From an inspection of Figures 2 and 3, it will be observed that thechoke valve shaft 32 is disposed materially below the center of thediscshaped choke valve 30 when the valve is in closed position, and thatthe carburetor air intake is provided with opposite straight portionsand I6 and offset horizontal shoulders 11 and 18 which permit thedisc-shaped valve member 38 to assume a horizontal position illustratedin Figure 3 when fully open, even though the shaft 32 is offset from thecenter of the disc-shaped valve member. This construction provides anunbalanced valve which atmospheric pressure outside of the carburetorwill tend to open to admit air to the carburetor through the air intake25 when the vacuum in the carburetor reaches a-predetermined limit. I

The operation of the device is as follows: Assuming that the engine iscold and that it is desired to start the same, under the condition of acold engine the thermostat 35 will tend to unwind and move the arm 45,the link 55 and the arm 34 to close the choke valve 30. The connection61, however, between the lever arm 34 andthe throttle lever 2'! willmaintain the choke valve 30 in a slightly open position as long as thecarburetor throttle is closed. Therefore, in order to obtain easystarting the manual control of the carburetor throttle must be actuatedto open the throttle a slight amount and relieve the tension on the link61 to permit the choke valve 30 to close. The engine can now be startedwith the throttle valve slightly open and the choke valve in its fullyclosed position. If, after the engine has been started, the manualcontrol is actuated to close the carburetor throttle to cause the engineto idle and draw its fuel supply from the idling jet of the carburetor,the connection 61 and related parts will slightly open the choke valve30 to permit passage of suflicient air through the air intake 25 toprevent vacuum in the carburetor from being built up to a point at whichthe engine will draw fuel from the main carburetor jet as well as fromthe idling jet, and there- 'I'his block is provided with a transversebyprevent the fuel mixture from becoming sufflciently rich to cause theengine to load up and stop. If the manual control of the throttle valveis now actuated to move the valve from its-closed or idling positiontoward its open position, tension,

on the link 61 will first be relieved thereby placing the choke valve 30completely under the control of the thermostat 35. After the tension onthe member 51 has been relieved, the block 65 will slide along themember so that the throttle lever 21 no longer has any effect upon thechoke valve 30. As the throttle is new advanced toward open position,the thermostat 35 tends to hold the choke valve 30 toward its closedposition, but as the choke valve 30 is unbalanced by being mount-' edelf-center on the shaft 32, the atmospheric pressure upon the outer sideof the valve, caused by increasing vacuum within the carburetor chamber,will tend to open the valve against the resilient action of thethermostat to admit suflicient air for proper fuel combustion at anyengine speed within the operative range of the engine. As the thermostat35 is mounted upon the exhaust manifold of the engine in heattransferring relation therewith, as the engine approaches its normaloperating temperature heat will be transferred to the thermostat causingit to wind up and move the arm 45, link 55 and arm 34 in a direction tomove the choke valve toward its fully open position as illustrated inFigure 3.

The opening of the choke valve 30 caused by the link 61 is not a matterof extreme accuracy,

as it is simply necessary to admit a suflicient amount of air to thecarburetor to prevent a high vacuum being formed therein when the engineis idling. The degree of throttle opening which permits the choke valve30 to close is, however, chosen with considerable care as the lowestengine speed which will insure continued operation of the engine takinginto consideration the strength of the thermostat and the amount ofunbalance of the choke valve. The thermostat is so positioned inrelation to the choke valve that the angle be tween the arm 45 and thelink 55 when the choke valve is fully closed is sufllciently acute toafford a comparatively high initial resistance to opening of the chokevalve 30. Also the strength of the thermostat and the amount that theshaft 32 is offset from the center of the valve 30 must be carefullybalanced in order that just suflicient air will be admitted to thecarburetor to insure an explosive fuel mixture at the instant enginetemperature, and the air will be accurately metered for the entireoperative range of engine speeds and temperatures.- If the amount theshaft is off center is too great or if the-thermostat is too weak, thefuel mixture will tend to be too lean for proper starting results, andif, on the other hand, the thermostat is too strong orthe amount ofoffset of the shaft 30 is too small, there will be a tendency for-thethermostat to hold the valve 3!! closed and unduly limit the amount ofair flowing into the carburetor thereby causing too rich a mixture topermit the engine to run smoothly after it has been started. It has beenfound, however, that if the strength of the thermostat and the unbalanceof the valve 30 are in proper relation to each other, immediate startingand smooth subsequent operation of the engine are assured, and it hasalso been found that a. connection as illustrated between the throttlelever and the choke valve to cause a slight opening of the choke valvewhen the throttle is closed will prevent the choke from stopping theengine when it is idling at a comparatively low operating temperature.

Having now described my invention so that others skilled in the art mayclearly understand the same, what I desire to secure by Letters Patentis as follows:

The combination with an internal combustion engine having an intake andan exhaust manifold, and a carburetor connected to said intake manifoldhaving an air intake and a throttle valve, of an automatic control forsaid carburetor air intake comprising, a choke valve in said air intakeeccentrically mounted on a shaft journaled in said air intake, 2. doublearmed choke valve lever having a long and a short arm, on said shaft,

thermostat is below a predetermined limit, a twoarmed throttle valvelever and an over-travel connection between one arm of said throttlevalve lever and the short end of said choke valve lever to restrain saidthermostat from completely clos-' ing said choke valve when saidthrottle valve is 10 closed.

( EARL E. MOORE.

